The present invention is directed to a fastening arrangement for a blade to a rotor of a straw chopper, wherein a bolt is inserted into a blade hole in the blade and a plate hole in a mounting plate extending from the rotor whose end is connected to a retaining element that retains the bolt in the holes, but can be separated from the bolt.
In straw chopper attachment implements in use today (see DE 36 31 485 C) the blades of the chopper are pendulously supported with screws and stop nuts to mounting plates, that extend from the chopper rotor. In order to attain a certain quality of the chopper performance and to keep the power requirement of the chopper within limits, the blades, that are ground on both sides, are disassembled after approximately 100 to 200 hours of operation and reassembled after the blades have been inverted. After this operating time the edge of the knife is dull, as a rule, so that the length of cut grows and the power requirement increases considerably. After a further 100 to 200 hours of operation the old blades are replaced with new blades. During the attachment and removal of the screws the operator must rotate the screw with a wrench held in one hand and hold a wrench with the other hand with which he holds the nut against rotation.
A disadvantage of the fastening with screws and stop nuts lies in the great amount of time that is required for the replacement or the inversion of the blades. For this operation the standard is approximately four hours for a complete exchange for a combine with six straw walkers.
U.S. patent application Ser. No. 10/230,694, filed Aug. 29, 2002 discloses other fastening arrangements are proposed for the fastening of the blades of a straw chopper. In a first embodiment a bolt is inserted through holes in the blades and in the mounting plate and locked by a pin that can be inserted through a radial opening in the bolt. A spring draws the pin against a retaining element. In a second embodiment the pin is locked to the bolt. The bolt is inserted axially into the retaining element and rotated through 90xc2x0 into its locking position in which a spring draws the pin into a recess in the retaining element. This fastening arrangement relieves the service personnel the task of loosening and tightening the screws. The bolt and the retaining element are pendulously supported on the mounting plate. Therefore during the insertion of the pin or the bolt it becomes necessary to rotate the bolt or the retaining element in order to bring it into a position in which the elements can be inserted into the associated openings. Furthermore a tool is required to compress the spring in order to be able to rotate the bolt between the releasing and locking position.
The problem underlying the invention is seen in the need to define an improved fastening arrangement for blades on a chopper rotor.
It is proposed that the bolt and/or the retaining element be connected, fixed against rotation, in the mounting plate relative to the direction of the axis of the hole in the mounting plate directly or indirectly. Thereby the bolt or the retaining element cannot rotate about their longitudinal axis relative to the mounting plate. In the locked position as a rule the bolt as well as the retaining element are connected to the mounting plate, fixed against rotationxe2x80x94that is, in each case the element fixed against rotation relative to the mounting plate.
In this way the result is a defined azimuthal orientation of the retaining element and/or of the bolt relative to the mounting plate. If the retaining element and the bolt are moved by a relative rotation between the loosening and the locked position, it is no longer necessary to hold in the retaining element or the fixed bolts, while the bolt or the retaining element is rotated. In an embodiment with a pin that can be inserted into the bolt and that is used to connect the bolt and the retaining element, which is forced into the locked position by the force of a spring, the result is a defined azimuthal orientation of the bolt and/or the retaining element, so that upon the insertion of the pin a rotation of these elements can be omitted which would have brought these into an orientation in which the pin can be inserted. This is useful particularly if the pin can be inserted only with a certain orientation of the bolt and the retaining element. The inverting or the replacement of the blades can be performed considerably simpler and faster.
Fundamentally it does not matter whether the bolt or the retaining element is connected to the mounting plate, to be fixed against rotation. For example, the bolt may be a screw with a four-sided shank that extends through a square hole in the mounting plate. At its end away from its head a nut is then screwed onto a thread as retaining element. In another embodiment the retaining element is connected to the mounting plate, fixed against rotation. For this purpose a part of the retaining element that can be inserted into the hole of the mounting plate and the hole itself in the mounting plate are equipped with matching non-circular cross sections. The cross sections may, for example, be elliptical or rectangular, particularly square. In this embodiment the bolt is connected to the retaining element, for example, by a screw thread, so that it can be removed.
In the last named embodiment the bolt can extend through an axial opening in the retaining element and can be connected with the retaining element, particularly on its outer side.
The blade or blades that is or are pendulously suspended in a manner known in itself are preferably supported in bearings on sleeves that enclose the retaining element or the bolt. The use of the sleeves makes it possible to replace in the case of excessive wear without any excessive cost the bearing surfaces on which the blades rotate, and that wear down gradually during the operation of the chopper. Most appropriately the sleeves are connected with the mounting plate, fixed against rotation, in order to prevent their rotation relative to the mounting plate and bring about a separation of the retaining element and the bolt.
The bolt that can be inserted through the mounting plate of the rotor and the blade hole in the blade can preferably be moved between a released position and a locked position by a rotation relative to the retaining element, where it does not matter whether the bolt or the retaining element is the one that is rotated. In the release position the retaining element can be separated from the bolt and mounted on it. In the locked position the retaining element cannot be separated from the bolt. An attachment of the retaining element to the bolt by means of a screw thread would be conceivable but has the disadvantage that the assembly and disassembly is relatively time consuming. Therefore it is proposed that the bolt and the retaining element can be moved between the release position and the locked position by a rotation through less than 360xc2x0. For this purpose a type of bayonet fastening can be provided between the retaining element and the bolt.
Preferably the retaining element and the bolt are retained by a spring in the locked position. For the inversion or the replacement of the blades the force of the spring must first be overcome in order to bring the retaining element and the bolt into the release position. With appropriate dimensioning of the spring an unintended release of the fastening arrangement need not be feared.
The arresting of the bolt at the retaining element can be performed in various ways. It would be possible, for example, to use a locking element extending radially from the bolt, where the bolt is moved between release position and locked position by rotation about its axis. The locking element is retained by a spring in the locked position in which it is forced against the retaining element, particularly into a recess arranged at that location. In the release position the bolt can be extracted axially through an opening provided at that location. The embodiment described here is disclosed in greater detail in U.S. patent application Ser. No. 10/230,694 filed Aug. 29, 2002, whose teaching is incorporated into the present disclosure by reference. This makes possible a simple and rapid locking of the fastening arrangement, however it is necessary to pre-load the spring, for which corresponding tools are required. In a preferred further development of the invention it is therefore proposed that the retaining element be provided with a helically shaped surface which is in contact with the locking element that is connected with the bolt. The helically shaped surface has the effect of operating in the form of a screw so that the spring is loaded or released when the bolt is rotated. A separate tool for loading the spring can be omitted, so that only a single tool is required for the rotation of the bolt.
In the locking position the locking element is preferably located in a recess at the end of the helical surface. The spring draws, presses or rotates the locking element into the recess. It is there arrested, fixed against rotation about its axis. The recess is preferably only so deep and/or chamfered in such a way that the bolt can be rotated into the loosened position in order to unload the spring without the use of any tool.
The bolt is inserted most appropriately into the retaining element in the axial direction. For this purpose the retaining element is provided with an axial opening that conforms to the cross section of the bolt to which the locking element is fastened.